JPH0347603A - Production of aluminum or aluminum alloy having excellent adhesive property of coating film - Google Patents

Abstract

PURPOSE:To improve the adhesive property of oil films and corrosion resistance by executing rolling with rolling rolls having patterned surfaces to form specific microholes on the surface at a specific hole occupying area rate. CONSTITUTION:The Al or Al alloy material is rolled by the rolling rolls having the patterned surfaces and is thereby formed with micropores of >=200Angstrom diameter and <=5mum depth on the surface at 5 to 60% hole occupying area rate. The adhesive property of the oil film on the Al or Al alloy material is good and the workability thereof is improved in this way.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is applicable to can ends (upper plates of cans) or can bodies (can bodies) of beverage cans, food cans, etc., which have strict requirements for coating film adhesion.
The present invention relates to a method for producing an aluminum or aluminum alloy material with excellent coating film adhesion and suitable for caps of containers (can bodies) and containers.

(Prior Art) Aluminum or aluminum alloy (hereinafter simply referred to as aluminum) coated plates have been used for beverage cans, food cans, container caps, building materials, structural materials, automobile materials, and the like. In such applications, the surface treatment method is as follows:
■Chemical conversion treatment that creates a chemical film using a treatment bath containing chromate or zirconate after degreasing and etching;
(2) Anodization treatment in various solutions such as sulfuric acid; (2) Boehmite treatment in which a hydrated oxide film of aluminum is generated in high-temperature water or in an aqueous solution to which an amine or the like is added.

Various types of surface treatment methods can be used depending on the purpose. In particular, for beverage cans, food cans, and container caps, chemical conversion treatment using a treatment bath containing chromate or zirconate is common, and the main purpose is to improve paint film adhesion and corrosion resistance.

(Problems to be Solved by the Invention) Beverage cans, food cans, and containers usually require high-temperature sterilization treatment (retort treatment) after filling with contents. but,
When the above-mentioned high temperature sterilization treatment is performed, the coating film on the cap may have good adhesion (initial adhesion) before treatment, but after treatment, the adhesion (secondary adhesion) often becomes poor (in extreme cases). This caused peeling of the paint film and a decrease in corrosion resistance, hygienic problems due to contamination of the can material into the contents, and leakage of the contents to the outside due to the formation of pinholes.

In addition, in the case of can ends (top plates for beverage cans, food cans, etc.), as shown in Figs. When removing the score 8 with the tab 9, the edge coating film piece 11
There was a problem that it peeled off and remained. The occurrence of this phenomenon is called poor feathering, and it is also influenced by the type of paint applied after the base treatment, and is particularly bad when using vinyl chloride resin paint.

On the other hand, in recent years, with the increasing variety of food products and the diversification of tastes, there has been an increasing need to fill the packaging with highly chlorine-containing substances that are highly corrosive to aluminum. Improved corrosion resistance is required.

In addition, anodic oxidation has been conventionally performed to improve the adhesion of aluminum materials to coatings, but the pores in the anodic oxide film are long and narrow, which causes cracks in the film when exposed to high temperatures. In addition, the conventional method for enlarging the pore size of an anodized film is the so-called pore-expanding treatment in which the fine pores are enlarged by dipping it in a highly soluble solution, such as a strong acid or strong alkaline solution, after anodizing, but this method is only inferior in productivity. However, the adhesion and workability of the paint film were still not satisfactory.

The present invention has been made for the purpose of solving the above-mentioned problems of the prior art and providing a method for manufacturing an aluminum material with excellent coating film adhesion.

(Means for Solving the Problems) That is, the present invention (1) performs rolling with a rolling roll having a patterned surface, and forms micropores with a diameter of 200 Å or more and a depth of 5 μm or less on the surface with a hole occupation area ratio of 5 to 60. %, (2) the method of producing an aluminum material having excellent paint film adhesion, (2) the method of (1), wherein the aluminum material is for can-end use, and (3) the aluminum material is vinyl chloride. It is the base for applying resin-based paint (1
) provides a method for manufacturing the item.

In the present invention, forming specific micropores on the surface of the aluminum material increases the actual surface area relative to the apparent surface area,
This is to increase the adhesion area of the paint, and to improve the adhesion of the paint film due to the anchor effect caused by the paint penetrating into the micropores.

The reason why the diameter of the micropores formed on the surface of the aluminum material is set to 200 Å or more is because the paint will not sufficiently penetrate into the holes if there are fewer than 200 people. Since the shape of these micropores is not necessarily circular, the pore diameter refers to the diameter when the area of the pore surface is replaced with a circle equivalent to the area (circular equivalent diameter). If the diameter of the micropores is too large, the actual surface area cannot be expected to increase much, so 200 to 3000 people is preferable.

The reason why the depth is set to 5 μm or less is that if the depth exceeds 5 μm, defects such as cracks are likely to occur in the coating film during molding after painting. However, if it is too shallow, the desired anchoring effect may not be obtained, so preferably 0.02 to 3
Let it be μm.

Furthermore, in the present invention, the pore occupied area ratio is set to 5 to 60%, and this pore occupied area ratio is the ratio (%) of the total opening area of the pores to the total surface area when the aluminum material surface is assumed to be flat. say. This is because if this value is less than 5%, the actual surface area cannot be expected to increase much, and if it exceeds 60%, there will be more spaces on the aluminum surface and the strength of the surface layer will decrease, resulting in poor paint film adhesion. Therefore, it is preferably 20 to 50%.

As a means of obtaining the above-mentioned surface shape of the aluminum material, the shape is transferred to the surface using a rolling roll with a patterned surface.This surface patterning refers to the process of forming micropores with the above-mentioned conditions on the aluminum material. The purpose is to form convex portions on the roll surface to enable transfer. In rolling with this rolling roll, the rolling reduction ratio is preferably 20% or less. If the rolling reduction ratio is 20% or less, the shape of the patterned rolling roll will be more accurately transferred to the aluminum material surface, and the surface shape will be uniform. Therefore, it is easy to obtain the desired surface shape. As a result, the adhesion of the coating film can be further improved.

In the present invention, the rolling roll may be a commonly used steel roll, and methods of forming a pattern on the roll surface include etching with corrosive liquid, electrical discharge machining, laser machining, ion beam etching, and the like.

In addition, after the desired surface is formed by transfer by main rolling, chemical conversion treatment in which a chemical film is generated in a treatment bath containing chromate or zirconate, or anodization treatment in various solutions such as sulfuric acid or phosphoric acid are performed. Further, by performing a boehmite treatment to generate a hydrated oxide film of aluminum in high-temperature water or an aqueous solution containing an amine or the like, it is possible to obtain even better adhesion (initial and secondary) and corrosion resistance.

Conventional surface treatments for painting include anodizing in sulfuric acid or phosphoric acid solutions as a means of forming micropores on the surface.
However, when using the method of the present invention, pores are formed directly on the material surface and the diameter of the pores is larger than that of the conventional method, allowing the paint to fully penetrate into the pores, resulting in greater adhesion. It is easy to process, economical, and has excellent quality stability.

The method of the present invention is particularly effective when an aluminum material is used as a base for a vinyl chloride resin paint, but it goes without saying that it is also sufficiently effective when using other paints.

The present invention is preferably applied to can ends for beverage cans, food cans, etc., but can bodies (can bodies), container caps, electronic devices, building materials, structural materials, automobile parts, etc. , adhesion, corrosion resistance, processability, productivity,
It can also be used for applications that require

(Example) Next, the present invention will be explained in more detail based on examples.

An aluminum plate (JIS A30B2-HI3) was rolled with rolling rolls A to F patterned to have the surfaces shown in Table 1, and finished to a plate thickness of 0.3 mm. The rolling reduction ratio is changed by controlling the plate thickness before rolling, and the rolling reduction ratio is always 0.3 mm after rolling.
Finished. This board was degreased using a commercially available neutral detergent and used as a sample for painting. Add 150mg/drr of commercially available vinyl chloride resin paint (vinyl chloride organosol paint) to this sample.
It was painted at a ratio of () and then baked at 280°C for 20 seconds.

Among the evaluation items, T-beer strength and feathering properties are tests related to the secondary adhesion of the paint film, and ERV is the enamel later value, which is an index of processability. The test method is as follows.

1) The method for preparing T-beer strength test pieces is shown in Figure 1, and the measuring method is shown in Figure 2. For baking, the sample was cut out to a size of 5 mm x 100 mm to form a test piece 1, a nylon film 2 was sandwiched between the test pieces 1 and 1, and heat and pressure bonding was performed using a hot press 3 at 200° C. for 30 seconds. The test piece was placed in pure water at 100℃ for 3
After being immersed for 0 ml, it was attached to a tensile testing machine and peeled off at a tensile speed of 200 mm/min as shown in Figure 2, and the peel strength was determined from the chart paper records at that time.Note 4
5 is an aluminum plate, and 5 is a coating film.

2) Feathering baking was performed by molding the subsequent sample into the upper plate (can end) 7 of the can 6 as shown in Fig. 3, and scoring 8. Tab 9 was installed. The test piece was immersed in pure water at 100° C. for 30 ml and then the tab 9 was pulled, and the form of the remaining coating film 11 in the opening 10 was investigated as shown in FIGS. 4(a) to (h). A rating number of 0 to 5 was assigned by visual observation depending on the degree of remaining coating film, and the smaller the rating number was judged to be better.

3) For ERV (enamel later value) baking, the sample is cut out to a size of 30 mm x 50 mm, and as shown in FIG. 5, the sample 12 is bent through two spacers 13 having the same plate thickness of 0.3 mm as the sample. On the other hand, as shown in FIG. 6, a 1% NaCβ solution 15 and a sponge 16 soaked in the solution are placed in a stainless steel container 14, and the bent portion of the sample 12 is set in contact with the sponge 16. Note that the width of the sponge 16 in contact with the sample 12 is 2 cm. Digital enamel later (manufactured by Pico)
At step 17, the electrodes are taken from the sample 12 and the stainless steel container 14, and the value of the flowing current is read. The higher the current value, the more defects in the coating film due to bending. Very good condition.

(Effects of the Invention) As explained above, the aluminum or aluminum alloy material produced by the method of the present invention has good coating film adhesion (initial and secondary) and excellent workability. Furthermore, the processing steps are simple, leading to a reduction in manufacturing costs.

[Brief explanation of drawings]

Figures 1 and 2 are schematic diagrams explaining the T beer strength test method, Figures 3 and 4 are diagrams explaining the feathering property test method, and Figures 5 and 6 are enamel later value test methods. FIG. Explanation of symbols 1...Test piece, 2...Nylon film, 3...
Hot press, 4... Aluminum plate, 5... Paint film, 6... Can, 7... Can end, 8... Score, 9... Tab, 10... Opening, 11 ... Paint film remaining, 12 ... Sample, 13 ... Spacer 14
...Container, 15...NaCj2 solution, 16...Sponge, enamel later 17...Digital ml plate (83Figure 2Figure 4Aluminum provisional 18-

Claims (3)

[Claims] (1) Rolling is performed using a rolling roll having a patterned surface to form micropores with a diameter of 200 Å or more and a depth of 5 μm or less on the surface with a pore occupied area ratio of 5 to 60%. A method for producing excellent aluminum or aluminum alloy materials. (2) The manufacturing method according to claim 1, wherein the aluminum or aluminum alloy material is for can ends. (3) The manufacturing method according to claim 1, wherein the aluminum or aluminum alloy material is a base coated with a vinyl chloride resin paint.